Syntax

Description

nag_lapack_zupgtr (f08gt) is intended to be used after a call to nag_lapack_zhptrd (f08gs), which reduces a complex Hermitian matrix AA to real symmetric tridiagonal form TT by a unitary similarity transformation: A = QTQHA=QTQH. nag_lapack_zhptrd (f08gs) represents the unitary matrix QQ as a product of n − 1n-1 elementary reflectors.

This function may be used to generate QQ explicitly as a square matrix.

Error Indicators and Warnings

It is possible that info refers to a parameter that is omitted from the MATLAB interface. This usually indicates that an error in one of the other input parameters has caused an incorrect value to be inferred.

Accuracy

The computed matrix QQ differs from an exactly unitary matrix by a matrix EE such that